661 USE OF PLATINUM FOR DETECTION OF ARSENIC. 
temperature for some time, and especially if in contact with 
alcohol and water, it gives rise to the formation of a certain 
quantity of the bichloride — corrosive sublimate. Hence he 
concludes, that it seems scarcely doubtful that this conver- 
sion is so much the more likely to be brought about in the 
organism, where it is subjected to a degree of heat approach- 
ing that necessary to effect the change (104° to 122° F.) in 
presence of the alkaline chlorides. 
ON THE DEVELOPMENT OE IODINE. 
Liebig states, that when the amount of iodine in combi- 
nation is so small that the usual starch test only furnishes a 
doubtful coloration, a more decided result will be obtained 
by the addition of a trace of alkaline iodates with a little 
hydrochloric acid ; a far greater quantity of iodine being 
liberated than existed in the iodate used. He has also found 
that starch water and hydrochloric acid alone, will often 
give a blue colour as deep as that obtained by means of 
chlorated water and hyponitric acid. 
ON THE USE OE PLATINUM INSTEAD OE PORCELAIN OR 
GLASS, IN MARSH’S METHOD OE DETECTING ARSENIC. 
Dr. Edmund Davy finds that a platinum spatula held 
over the burning jet of arseniuretted hydrogen, as given off 
from Marsh’s apparatus, is preferable to a piece of porcelain 
or glass, as usually recommended. 
Depending on the distance which the spatula is held from 
the flame so will the deposit be either metallic arsenic or 
arsenious acid. If near, the former ; if a little way off, the 
latter. The metallic arsenic adheres firmly to the platinum, 
but the heat of a candle is sufficient to volatilize it, when it is 
accompanied w 7 ith its characteristic alliaceous odour, even 
when the quantity of arsenicum is less than the one-thou- 
sandth part of a grain. 
If antimoniuretted h}ffirogen be inflamed and treated in the 
same way, blackish spots of antimony are deposited, which 
are not removed by the flame of a candle. 
He further adds : 
66 The advantages of the plantinum surface over porcelain 
or glass appear to be pretty obvious. The former is more 
manageable for subsequent experiments. The arsenic 
strongly adheres to platinum, but weakly to glass or porce- 
lain, from which surfaces it is easily removed by the finger. 
It is readily sublimed, producing the garlic-odour. There is 
